The OpenWrite method returns a writable stream that is used to send data to a resource. The underlying request is made with the method specified in the method parameter. The data is sent to the server when you close the stream. This method blocks while opening the stream. To continue executing while waiting for the stream, use one of the OpenWriteAsync methods.

If the method parameter specifies a method that is not understood by the server, the underlying protocol classes determine what occurs. Typically, a WebException is thrown with the Status property set to indicate the error.

If the BaseAddress property is not an empty string ("") and address does not specify an absolute address, address must be a relative URI that is combined with BaseAddress to form the absolute URI of the requested data. If the QueryString property is not an empty string, it is appended to address.